Three-Dimensional Finite Research Articles

An Inverse Approach for Evaluating the Properties of Asphalt Concrete Using the APA Test

ABSTRACT Rutting is one of the most serious distresses for asphalt pavement. The occurrence of rutting affects the performance of the pavement. Simulative tests including Asphalt Pavement Analyzer (APA) tests have been widely used to evaluate the rutting potential of Asphalt Concrete (AC). However, they usually cannot give fundamental properties of AC due to the complex stress and strain fields. In this study, a computational simulation method for the A PA test was developed to predict the rutting potential of AC through a viscoplasticity model and three-dimensional (3D) Finite Element Method (FEM). The model material parameters such as the elasticity modulus, yielding stress, and rutting factor (f) were obtained through an inverse method. Sensitivity of the material parameters on the influence of the rutting behavior was also evaluated. The comparison between A PA test results and the model simulation indicates that the model can capture rutting behavior of AC very well. The inverse technique enables characterization of fundamental material properties through simulative tests and saves tremendous efforts for calibration of advanced models. The computational simulative test also makes it possible to simulate rutting tests at different scales.

Local strain energy approach applied to fatigue analysis of welded rectangular hollow section joints

This paper deals with fatigue life assessments of welded rectangular hollow sections made of steels and aluminium alloys, in a T-joint configuration, carried out by means of a local stress approach. The welded toe region is modelled like a sharp V-notch with an opening angle of 135 and the intensity of the asymptotic stress distributions is quantified by means of the Notch Stress Intensity Factors (NSIFs). In order to carefully evaluate the NSIFs of hollow sections welded in a T-joint configuration, some Three-Dimensional (3D) Finite Element (FE) analyses are firstly carried out. Afterwards, the NSIFs are used to evaluate the mean value of the strain energy density over a semicircular sector of radius RC at the welded toe. The radius RC is thought of as a material-dependent parameter. The experimental values of fatigue life are compared with those predicted by two previously scatter bands curves recently reported in the literature for welded joints made of structural steel and aluminium alloy. These curves were drawn by using mainly fatigue data obtained from cruciform and T-shaped welded joints. Although the analyses reported here represent only a first attempt to extend an energy-based approach to 3D hollow section joints, the comparison shows that a quite satisfactory assessment of the fatigue life can also be obtained for this type of welded joints. The agreement is good for welded joints made of structural steel, whereas the predictions are found to be in the safe direction for welded joints made of aluminium.

3차원 강소성 유한요소법을 이용한 환상압연공정중 형상결함의 예측

3차원 강소성 유한요소법을 이용한 환상압연공정중 형상결함의 예측

Three-Dimensional Elastic-Plastic Finite Element Analysis of Biaxially Loaded Cracked Plates

Based on detailed two-dimensional (2-D) and three-dimensional (3-D) finite element (FE)analyses, this paper attempts to quantify in-plane and out-of-plane constraint effects on elastic-plastic J and cracked tip stresses for biaxially loaded plate with a through-thickness crack and semi-elliptical surface crack. It is found that the reference stress based approach for uniaxial loading can be applied to estimate J under biaxial loading, provided that the limit load specific to biaxial loading is used, implying that quantification of the biaxiality effect on the limit load is important. Investigation on the effect of biaxiality on the limit load suggests that for relatively thin plates with small cracks, in particular with semi-elliptical surface cracks, the effect of biaxiality on the limit load can be neglected, and thus elastic-plastic J for a biaxially loaded plate could be estimated, assuming that such plate is subject to uniaxial load. Regarding the effect of biaxiality on crack tip stress triaxiality, it is found that such effect is more pronounced for a thicker plate. For plates with semi-elliptical surface cracks, the crack aspect ratio is found to be more important than the relative crack depth, and the effect of biaxiality on crack tip stress triaxiality is found to be more pronounced near the surface points along the crack front.

Numerical differentiation of Laplacian 3-D FE solutions by using regular polyhedra quadrature of Poisson integrals

An efficient numerical procedure to compute accurately derivatives of three-dimensional (3-D) Finite Element (FE) solutions to Laplacian electromagnetic problems is presented. The technique adopted is based on the combined use of Poisson Integrals and an innovative quadrature approach, exploiting symmetry properties by using as integration points vertices of regular polyhedra. The postprocessing procedure gets highly accurate results with a modest computational effort if compared with standard integration techniques. It has been found by comparison against known analytical functions that only few points are needed to reach a high degree of accuracy.

Development of Three-Dimensional Layered Finite Element for Thermo-Mechanical Analysis

Development of Three-Dimensional Layered Finite Element for Thermo-Mechanical Analysis

Simulation of the Hot Ring Rolling Process by Using a Thermo-Coupled Three-Dimensional Rigid-Viscoplastic Finite Element Method

During hot metal forming, the temperature variation and plastic deformation affect each other considerably. In the present investigation, ring rolling of hot steel is simulated by using a three-dimensional thermo-coupled rigid-viscoplastic finite element method. A new term is added to the functional in the variational approach to consider the influence of the frictional torque of the mandrel bearing, and the coupled thermal-mechanical simulation is performed by the iteration between the rigid-viscoplastic finite element analysis and the thermal finite element analysis. Since the deformation region and the severe temperature changes are restricted to the vicinity of the roll gap, only a ring segment and parts of the rolls are analyzed using a steady-state treatment to save computation time. Roll force and torque, width spread, temperature distributions, the distributions of strain and strain rate and the distributions of relative velocity and stress at the roll surfaces are obtained. The results show that the angular velocity of the driven roll has a significant influence on the temperature variations in the ring and the rolls, to which attention should be paid in the design of the process. The method presented can also be used to analyze other forming processes such as unsymmetrical plate rolling, symmetric rolling, and extrusion.

Investigation of the Cogging Process by Three-Dimensional Thermo-Viscoplastic Finite Element Analysis

The purpose of cogging in open-die press forging is to maximize the internal deformation for better structural homogeneity and centre-line consolidation in the core of the ingot. A three-dimensional thermo-viscoplastic finite element analysis is carried out for the non-isothermal cogging process in order to study the distribution of hydrostatic stresses, effective strains and temperature of the ingot and the die during the process. In the simulation, V-die and flat-die are employed for computation. A circular ingot of body weight 160 ton is subjected to cogging simulation and the effects of cogging parameters, such as die configuration, die width, temperature gradient, height reduction and draft design, are compared between two types of dies. Thus favourable working conditions are suggested for better and more desirable product quality.

Three-dimensional finite, boundary, and hybrid element solutions of the Maxwell equations for lossy dielectric media

Finite, boundary, and hybrid element approaches are presented as numerical methods for computing electromagnetic (EM) fields inside lossy dielectric objects. These techniques are implemented as computer algorithms for solving the Maxwell equations in heterogeneous media in three dimensions. Algorithm verification takes the form of comparisons of test cases with analytic solutions. Computed results for each technique are in good agreement with exact solutions, especially in light of the coarse computational grid resolutions used. Implementation was in FORTRAN on a moderate-sized computer (MicroVax II). The basic problem formulation is quite general; however, it has direct application in hyperthermia as a cancer therapy where the EM fields produced inside the patient by external sources are of interest. An example of the application of these numerical methods in a three-dimensional clinical setting is shown. >